“We wanted to see how important EDVs may be over the next 40 years in terms of their ability to reduce emissions,” senior author Dr. Joseph DeCarolis, an assistant professor of civil, construction and environmental engineering at NC State, explained in a statement. “We found that increasing the use of EDVs is not an effective way to produce large emissions reductions.”

Dr. DeCarolis and his colleagues conducted a total of 108 different scenarios in order to determine the impact of EDVs on emissions between now and 2050. Those scenarios were based on a variety of assumptions related on the cost of crude oil and natural gas, CO2 emissions policies, and vehicle battery cost. They concluded that even if EDVs comprised 42 percent of all passenger vehicles, there would be little to no reduction in air pollutant emissions.

“There are a number of reasons for this,” DeCarolis said. “In part, it’s because some of the benefits of EDVs are wiped out by higher emissions from power plants. Another factor is that passenger vehicles make up a relatively small share of total emissions, limiting the potential impact of EDVs in the first place. For example, passenger vehicles make up only 20 percent of carbon dioxide emissions.”

“From a policy standpoint, this study tells us that it makes more sense to set emissions reductions goals, rather than promoting specific vehicle technologies with the idea that they’ll solve the problem on their own,” he continued, noting that the energy systems model also showed oil price and battery cost are the primary factors in encouraging consumers to use EDVs. “That’s consistent with results from other studies,” he added.

The study authors say the results of their simulations did not demonstrate a clear, consistent trend toward lower system-wide emissions with increases in the number of hybrid or electric vehicles on the roadways. In addition to the trade-off between lower tailpipe emissions and higher electric sector emissions associated with plug-in hybrids, the scenarios produced across the board emissions effects that tended to mask the positive effects.